Polyester resin blend

ABSTRACT

The present disclosure relates to a polyester resin blend. The polyester resin blend can provide a thick container with high transparency even if it contains recycled polyethylene terephthalate as well as virgin polyethylene terephthalate. In addition, the resin blend can be reused by itself, and is expected to be useful for providing continuously usable plastics that have been recently attracting attention.

TECHNICAL FIELD

The present disclosure relates to a polyester resin blend.

BACKGROUND OF ART

Waste plastics, which account for about 70% of marine pollution, haverecently emerged as a serious social problem, and each country regulatesthe use of disposable plastics while promoting reuse of waste plastics.Currently, waste plastics are collected, crushed and washed, and thenmelt-extruded and re-pelletized to be reused as raw materials. However,it is very difficult to provide good-quality plastic products due toforeign substances in the waste plastics. Accordingly, research onproducing good-quality plastic products from waste plastics is urgentlyneeded.

PRIOR ART DOCUMENTS Patent Documents

-   Japanese Patent No. 4771204

DETAILED DESCRIPTION OF THE INVENTION Technical Problem

The present disclosure is to provide a reusable polyester resin blendcapable of providing a thick container with high transparency.

Technical Solution

In the present disclosure, there is provided a polyester resin blendincluding polyethylene terephthalate; and a polyester resin having astructure in which an acid moiety derived from a dicarboxylic acid or aderivative thereof and a diol moiety derived from a diol are repeated bypolymerizing a dicarboxylic acid or a derivative thereof and a diolcontaining ethylene glycol and a comonomer, wherein the polyester resinincludes 5 to 20 mol % of a diol moiety derived from a comonomer withrespect to the total diol moiety derived from a diol, and the comonomercomprises isosorbide.

Advantageous Effects

The polyester resin blend according to an embodiment of the presentdisclosure can provide a thick container with high transparency even ifit contains recycled polyethylene terephthalate as well as virginpolyethylene terephthalate. In addition, the resin blend can be reusedby itself, and is expected to be useful for providing continuouslyusable plastics that have been recently attracting attention.

Detailed Description of the Embodiments

Hereinafter, the polyester resin blend according to a specificembodiment of the present disclosure will be described.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention.The singular forms are intended to include the plural forms as well,unless the context clearly indicates otherwise. The terms “include”,“comprise”, and the like of the present disclosure are used to specifycertain features, regions, integers, steps, operations, elements, and/orcomponents, and these do not exclude the existence or the addition ofother certain features, regions, integers, steps, operations, elements,and/or components.

According to an embodiment of the present disclosure, there is provideda polyester resin blend including polyethylene terephthalate; and apolyester resin having a structure in which an acid moiety derived froma dicarboxylic acid or a derivative thereof and a diol moiety derivedfrom a diol are repeated by polymerizing a dicarboxylic acid or aderivative thereof and a diol containing ethylene glycol and acomonomer, wherein the polyester resin includes 5 to 20 mol % of a diolmoiety derived from a comonomer with respect to the total diol moietyderived from a diol, and the comonomer comprises isosorbide.

The polyethylene terephthalate is widely used commercially due to itslow price and excellent physical/chemical properties, but it has highcrystallinity.

Therefore, it requires a high temperature during processing, and has alimitation in providing a transparent product due to its highcrystallization rate.

The present inventors have researched to solve this problem, and foundthat blending polyester terephthalate with a polyester resin containinga diol moiety derived from a comonomer including isosorbide can providea reusable polyester resin blend capable of providing a thick containerwith high transparency.

Hereinafter, the polyester resin blend will be described in detail.

The polyester resin according to the embodiment may be blended withvarious general-purpose polyethylene terephthalates to control itscrystallinity and crystallization rate to an appropriate level, therebyproviding a thick container with high transparency.

Accordingly, the type of the polyethylene terephthalate is notparticularly limited. For example, the polyethylene terephthalate isprepared by polymerizing a dicarboxylic acid or a derivative thereof anda diol, and the dicarboxylic acid or a derivative thereof may be mainlyterephthalic acid or a derivative thereof and the diol may be mainlyethylene glycol.

As used herein, the term ‘dicarboxylic acid or a derivative thereof’means at least one compound selected from a dicarboxylic acid andderivatives of the dicarboxylic acid. In addition, the term ‘derivativeof the dicarboxylic acid’ means an alkyl ester of dicarboxylic acid (C1to C4 lower alkyl ester such as monomethyl ester, monoethyl ester,dimethyl ester, diethyl ester, dibutyl ester, or the like) or adicarboxylic acid anhydride. Accordingly, for example, the terephthalicacid or the derivative thereof commonly includes a compound that reactswith a diol to form a terephthaloyl moiety, such as terephthalic acid;monoalkyl or dialkyl terephthalate; and terephthalic acid anhydride.

The polyethylene terephthalate may include a residue derived from acomonomer other than terephthalic acid or a derivative thereof.Specifically, the comonomer may be at least one selected from the groupconsisting of a C8-C14 aromatic dicarboxylic acid or a derivativethereof, and a C4-C12 aliphatic dicarboxylic acid or a derivativethereof. Examples of the C8-C14 aromatic dicarboxylic acid or thederivative thereof may include aromatic dicarboxylic acids orderivatives thereof that are generally used in manufacture of thepolyester resin, for example, naphthalene dicarboxylic acid such asisophthalic acid, dimethyl isophthalate, phthalic acid, dimethylphthalate, phthalic acid anhydride, 2,6-naphthalene dicarboxylic acid,etc., dialkylnaphthalene dicarboxylate such as dimethyl 2,6-naphthalenedicarboxylate, etc., diphenyl dicarboxylic acid, etc. Examples of theC4-C12 aliphatic dicarboxylic acid or the derivative thereof may includelinear, branched or cyclic aliphatic dicarboxylic acids or derivativesthereof that are generally used in manufacture of the polyester resin,for example, cyclohexane dicarboxylic acid such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexane dicarboxylic acid, etc., cyclohexanedicarboxylate such as dimethyl 1,4-cyclohexane dicarboxylate, dimethyl1,3-cyclohexane dicarboxylate, etc., sebacic acid, succinic acid,isodecylsuccinic acid, maleic acid, maleic anhydride, fumaric acid,adipic acid, glutaric acid, azelaic acid, etc. The comonomer may be usedin an amount of 0 to 50 mol %, 0 mol % to 30 mol %, 0 to 20 mol % or 0to 10 mol % with respect to the total dicarboxylic acid or thederivative thereof.

The polyethylene terephthalate may include a residue derived from acomonomer other than ethylene glycol. Specifically, the comonomer may bea C8-C40, or C8-C33 aromatic diol, a C2-C20, or C2-C12 aliphatic diol,or a mixture thereof. Examples of the aromatic diol may include ethyleneoxide and/or propylene oxide-added bisphenol A derivatives such aspolyoxyethylene-(2.0)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene-(2.0)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene-(2.2)-polyoxyethylene-(2.0)-2,2-bis(4-hydroxyphenyl)propane,polyoxyethylene-(2.3)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene-(6)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene-(2.3)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene-(2.4)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene-(3.3)-2,2-bis(4-hydroxyphenyl)propane,polyoxyethylene-(3.0)-2,2-bis(4-hydroxyphenyl)propane, orpolyoxyethylene-(6)-2,2-bis(4-hydroxyphenyl)propane(polyoxyethylene-(n)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene-(n)-2,2-bis(4-hydroxyphenyl)propane, orpolyoxypropylene-(n)-polyoxyethylene-(n)-2,2-bis(4-hydroxyphenyl)propane,wherein n is the number of polyoxyethylene or polyoxypropylene units).Examples of the aliphatic diol may include linear, branched or cyclicaliphatic diols such as diethylene glycol, triethylene glycol,propanediol (1,2-propanediol, 1,3-propanediol, etc.), 1,4-butanediol,pentanediol, hexanediol (1,6-hexanediol, etc.), neopentyl glycol(2,2-dimethyl-1,3-propanediol), 1,2-cyclohexanediol,1,4-cyclohexanediol, 1,2-cyclohexanedimethanol,1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tetramethylcyclobutanediol, etc. The comonomer may be used in an amount of 0 to 50mol %, 0 mol % to 30 mol %, 0 to 20 mol % or 0 to 10 mol % with respectto the total diol.

The polyester resin according to the above embodiment may not onlysupplement physical properties of virgin polyethylene terephthalate, butalso supplement reduced physical properties of recycled polyethyleneterephthalate to a very good level.

The recycled polyethylene terephthalate can be understood to includepolyethylene terephthalate collected after use or all obtainedtherefrom. Specifically, the recycled polyethylene terephthalate may beobtained by separating the collected waste plastics according to acertain standard, pulverizing and washing them and then re-pelletizingthem by melt extrusion, or may be obtained by depolymerizing thecollected waste plastics to a monomer level and repolymerizing them. Therecycled polyethylene terephthalate may be used after re-pelletizationand crystallization, or after further polycondensation in a solid stateafter crystallization depending on a processing method.

The recycled polyethylene terephthalate repolymerized by depolymerizingwaste plastics to a monomer level may exhibit good properties that arenot easily distinguishable from virgin polyethylene terephthalate.However, recycled polyethylene terephthalate obtained byre-pelletization of waste plastics is less transparent than virginpolyethylene terephthalate and has a very fast crystallization rate,making it difficult to produce transparent containers having anappropriate thickness, even if the recycled polyethylene terephthalateis used alone or mixed with virgin polyethylene terephthalate. However,the polyester resin according to an embodiment exhibits excellentmiscibility with the recycled polyethylene terephthalate, therebyproviding a thick container with high transparency. In particular, thepolyester resin according to an embodiment can provide a molded articlehaving no flow-mark on the surface without other additives, because itis highly miscible with recycled polyethylene terephthalate.

Accordingly, virgin polyethylene terephthalate, recycled polyethyleneterephthalate, or a mixture thereof may be used as the polyethyleneterephthalate.

In particular, the polyester resin according to an embodiment mayexhibit excellent processability with a resin having an intrinsicviscosity of 0.6 to 0.8 dVg among the recycled polyethyleneterephthalate.

In addition, the polyester resin according to the above embodiment maybe useful for recycling of a resin containing 95 mol % or more of aresidue derived from terephthalic acid and 95 mol % or more of a residuederived from ethylene glycol among the recycled polyethyleneterephthalate. Since the resin may be a homopolymer made of terephthalicacid and ethylene glycol, the upper limits of the residue derived fromterephthalic acid and the residue derived from ethylene glycol are 100mol %. When the residue derived from terephthalic acid and the residuederived from ethylene glycol are less than 100 mol %, a residue derivedfrom the comonomer described above may be included within 5 mol %.Specifically, a residue derived from isophthalic acid and/or a residuederived from cyclohexanedimethanol may be included within 5 mol %,respectively.

The polyester resin may be blended with recycled polyethyleneterephthalate having a crystallization temperature of 130° C. to 160° C.to effectively control a crystallization rate of the recycledpolyethylene terephthalate.

The polyester resin may be blended with recycled polyethyleneterephthalate having a melting temperature of 250° C. or higher toprovide a polyester resin blend having a melting temperature that iseasy to process.

The polyester resin according to the embodiment may be a crystallineresin.

In particular, the polyester resin may be a resin having crystallinitysuch that it does not fuse with each other even when dried at a hightemperature with the polyethylene terephthalate. Specifically, a passingrate may be 97 wt % or more, 98 wt % or more, or 99 wt % or more whenthe polyethylene terephthalate and the polyester resin are pelletized tobe 80 pieces per 1 g each, dried at a temperature of 160° C. for 1 hour,and then passed through a sieve having a sieve size of 2.36 mm. Thesieve size refers to the longest length of the hole.

As the polyester resin according to the embodiment has suchcrystallinity, the blend blended with polyethylene terephthalate can bereused, unlike the amorphous resin. Accordingly, when the polyesterresin is used, not only the waste plastics can be reused, but also areusable plastic product can be provided.

It is advantageous for the polyester resin to have high transparency toprovide a highly transparent molded article by blending withpolyethylene terephthalate. Specifically, the polyester resin may have ahaze of 5% or less, 4.5% or less, 4% or less, 3.5% or less, 3% or less,2.5% or less, or 2% or less, when measured for a 6 mm thick specimenaccording to ASTM D1003-97. As the haze is most preferably 0% in theory,the lower limit may be 0% or more.

The polyester resin may have a melting temperature of 210 to 245° C.,220 to 240° C. or 230 to 235° C. when measured after crystallization at180° C. for 100 minutes, so that it can be blended with polyethyleneterephthalate and processed at an appropriate temperature to provide amolded article having the characteristics described above.

The polyester resin may have a crystallization half-time of 7 to 95minutes, 7 to 80 minutes, 7 to 70 minutes, 7 to 60 minutes, 10 to 95minutes, 30 to 95 minutes, to 95 minutes, 10 to 80 minutes, 30 to 70minutes, 30 to 60 minutes or 40 to 60 minutes, so that it can be blendedwith polyethylene terephthalate and processed at an appropriatetemperature to provide a molded article having the characteristicsdescribed above.

The polyester resin is obtained by polymerizing a dicarboxylic acid or aderivative thereof and a diol, and has a structure in which an acidmoiety derived from a dicarboxylic acid or a derivative thereof and adiol moiety derived from a diol are repeated. In the present disclosure,the acid moiety and the diol moiety refer to a residue remaining afterthe dicarboxylic acid or a derivative thereof and the diol arepolymerized to remove hydrogen, hydroxyl or alkoxy groups from them.

In particular, the polyester resin includes a diol moiety derived from adiol containing ethylene glycol and a comonomer, and the diol moietyderived from the comonomer may be included in 5 to 20 mol % with respectto the total diol moiety. Further, the comonomer may exhibit theabove-described properties as it includes isosorbide(1,4:3,6-dianhydroglucitol).

When the diol moiety derived from the comonomer is less than 5 mol %, itis difficult to provide a transparent molded article because the highcrystallization rate due to polyethylene terephthalate cannot beadjusted to an appropriate level. When the diol moiety derived from thecomonomer exceeds 20 mol %, the polyester resin exhibits amorphousnessand can be easily fused in a processing or molding process. In addition,miscibility with polyethylene terephthalate decreases, flow-marks mayoccur on the surface of the molded article, and the polyester resinblend cannot be reused.

The polyester resin may include 5 to 15 mol %, 7 to 15 mol %, 8 to 15mol % 10 to 15 mol %, 9 to 12 mol % or 10 to 12 mol % of the diol moietyderived from the comonomer with respect to the total diol moiety inorder to exhibit better miscibility with recycled polyethyleneterephthalate.

The polyester resin essentially includes a diol moiety derived fromisosorbide as a diol moiety derived from a comonomer, and this structuremakes it possible to manufacture a thick container with hightransparency by adjusting the crystallization rate of polyethyleneterephthalate to an appropriate level. Further, the polyester resin canbe reused even after being mixed with recycled polyethyleneterephthalate to provide a plastic that can be used continuously. On theother hand, referring to Comparative Example 5, which will be describedlater, a polyester resin including a diol moiety derived from acomonomer other than isosorbide exhibits good miscibility withpolyethylene terephthalate and shows good processability. However, thepolyester resin cannot provide a transparent product because it cannotcontrol the crystallization rate of polyethylene terephthalate to anappropriate level.

The polyester resin may include 0.1 to 15 mol %, in particular 0.1 to 10mol %, 0.1 to 9 mol %, 1 to 10 mol %, or 1 to 9 mol % of a diol moietyderived from isosorbide with respect to the total diol moiety tomaximize the properties described above.

Meanwhile, the comonomer other than ethylene glycol may further includecyclohexanedimethanol in addition to isosorbide. Thecyclohexanedimethanol may be used in an amount of 0.1 to 15 mol % withrespect to the total diol to provide the polyester resin having theabove-described properties.

When isosorbide and cyclohexanedimethanol are used as comonomers, theymay be used in a ratio of 1:2 to 5 mol, or 1:2 to 4 mol to ensure betterphysical properties.

The comonomer other than ethylene glycol may include a diol generallyused in manufacture of the polyester resin in addition to the monomersdescribed above. Specific examples of the diol may include diols listedthat can be used in the above-described polyethylene terephthalate.However, it is advantageous for the comonomer other than ethylene glycolto be isosorbide or a combination of isosorbide andcyclohexanedimethanol to satisfy the physical properties describedabove. When the comonomer includes a diol other than isosorbide andcyclohexanedimethanol, its content may be 10 mol % or less, 5 mol % orless, or 2 mol % or less with respect to the total comonomer.

In the polyester resin, a dicarboxylic acid or a derivative thereof maybe mainly terephthalic acid or a derivative thereof like polyethyleneterephthalate described above, and the polyester resin may include acomonomer other than terephthalic acid or a derivative thereof. The typeand content of the comonomer can be adjusted by referring to the typeand content of the comonomer that can be used for the above-describedpolyethylene terephthalate.

Meanwhile, the polyester resin may be prepared including the steps ofperforming an esterification reaction or a transesterification reactionon the above-described dicarboxylic acid or a derivative thereof and theabove-described diol; and performing a polycondensation reaction on aproduct obtained by the esterification or transesterification reaction.

A catalyst may be used in the esterification or transesterificationreaction. Such catalyst may include methylates of sodium and magnesium;acetates, borates, fatty acids, or carbonates of Zn, Cd, Mn, Co, Ca, Baand the like; metals such as Mg; and oxides of Pb, Zn, Sb, Ge and thelike.

The esterification or transesterification reaction may be carried out ina batch, semi-continuous or continuous manner. Each raw material may beadded separately, but it may preferably be added in a slurry form inwhich the dicarboxylic acid or the derivative thereof is mixed in thediol.

A polycondensation catalyst, a stabilizer, a coloring agent, acrystallizing agent, an antioxidant, a branching agent and the like maybe added in the slurry before the esterification or transesterificationreaction or in the product after completion of the reaction.

However, the input timing of the above-described additive is not limitedthereto, and the above-described additive may be added at any timeduring the preparation of the polyester resin. As the polycondensationcatalyst, at least one of conventional titanium, germanium, antimony,aluminum, tin-based compounds may be appropriately selected and used.Examples of the preferable titanium-based catalyst include tetraethyltitanate, acetyltripropyl titanate, tetrapropyl titanate, tetrabutyltitanate, polybutyl titanate, 2-ethylhexyl titanate, octylene glycoltitanate, lactate titanate, triethanolamine titanate, acetylacetonatetitanate, ethyl acetoacetic ester titanate, isostearyl titanate,titanium dioxide, titanium dioxide/silicon dioxide copolymer, titaniumdioxide/zirconium dioxide copolymer, and the like. In addition, examplesof the preferable germanium-based catalyst include germanium dioxide anda copolymer thereof. As the stabilizer, phosphorus-based compounds suchas phosphoric acid, trimethyl phosphate, and triethyl phosphate may begenerally used, and an added content thereof may be 10 to 200 ppm withrespect to a weight of the final polymer (polyester resin) based on aphosphorus atom. When the content of the stabilizer is less than 10 ppm,the polyester resin may not be sufficiently stabilized and a color ofthe polyester resin may become yellow. When the content is more than 200ppm, a polymer having a high degree of polymerization may not beobtained. Further, examples of the coloring agent to be added forimproving a color of the polymer may include conventional cobalt-basedcoloring agents such as cobalt acetate, cobalt propionate, and the like.An added content thereof may be 1 to 200 ppm with respect to a weight ofthe final polymer (polyester resin) based on a cobalt atom. Ifnecessary, anthraquionone-based compounds, perinone-based compounds,azo-based compounds, methine-based compounds, and the like may be usedas an organic coloring agent, and commercially available productsinclude toners such as Polysynthren Blue RLS (manufactured by Clarient)and Solvaperm Red BB (manufactured by Clarient). An added content of theorganic coloring agent may be 0 to 50 ppm with respect to a weight ofthe final polymer. When the coloring agent is used in the content out ofthe above-described range, a yellow color of the polyester resin may notbe sufficiently covered or physical properties may be reduced.

Examples of the crystallizing agent may include a crystal nucleatingagent, an ultraviolet absorber, a polyolefin-based resin, a polyamideresin, and the like. Examples of the antioxidant may include a hinderedphenolic antioxidant, a phosphite-based antioxidant, a thioether-basedantioxidant, and a mixture thereof. The branching agent is a commonbranching agent having at least three functional groups, and examplesthereof may include trimellitic anhydride, trimethylol propane,trimellitic acid, or a mixture thereof.

Moreover, the esterification reaction may be carried out at atemperature of 200 to 300° C. or 230 to 280° C., and under a pressure of0 to 10.0 kgf/cm² (0 to 7355.6 mmHg), 0 to 5.0 kgf/cm² (0 to 3677.8mmHg) or 0.1 to 3.0 kgf/cm² (73.6 to 2206.7 mmHg). And thetransesterification reaction may be carried out at a temperature of 150to 270° C. or 180 to 260° C., and under a pressure of 0 to 5.0 kgf/cm²(0 to 3677.8 mmHg) or 0.1 to 3.0 kgf/cm² (73.6 to 2206.7 mmHg). Thepressures outside the parentheses refer to gauge pressures (expressed inkgf/cm²) and the pressures inside parentheses refer to absolutepressures (expressed in mmHg).

When the reaction temperature and pressure are out of the above range,physical properties of the polyester resin may be lowered. The reactiontime (average residence time) is usually 1 to 24 hours, or 2 to 8 hours,and may vary depending on the reaction temperature, pressure, and molarratio of the diol to the dicarboxylic acid or the derivative thereofused.

The product obtained by the esterification or transesterificationreaction may be subjected to a polycondensation reaction to prepare apolyester resin having a high degree of polymerization. Generally, thepolycondensation reaction may be carried out at a temperature of 150 to300 IC, 200 to 290° C. or 260 to 290 IC, and under a reduced pressure of400 to 0.01 mmHg, 100 to 0.05 mmHg, or 10 to 0.1 mmHg. Herein, thepressures refer to absolute pressures. The reduced pressure of 400 to0.01 mmHg is for removing by-products of the polycondensation reactionsuch as glycol and unreacted materials such as isosorbide. Therefore,when the pressure is out of the above range, the removal of by-productsand unreacted materials may be insufficient. In addition, when thetemperature of the polycondensation reaction is out of the above range,physical properties of the polyester resin may be lowered. Thepolycondensation reaction may be carried out for the required time untilthe desired intrinsic viscosity is reached, for example, for an averageresidence time of 1 to 24 hours.

In order to reduce the content of the unreacted materials such asisosorbide remaining in the polyester resin, the unreacted raw materialsmay be discharged out of the system by intentionally maintaining thevacuum reaction for a long period of time at the end of theesterification reaction or the transesterification reaction or at thebeginning of the polycondensation reaction, that is, in a state in whichthe viscosity of the resin is not sufficiently high. When the viscosityof the resin is high, it is difficult for the raw materials remaining inthe reactor to flow out of the system. For example, the unreactedmaterials remaining in the polyester resin such as isosorbide may beremoved effectively by leaving the reaction products obtained by theesterification or transesterification reaction before thepolycondensation reaction for about 0.2 to 3 hours under a reducedpressure of about 400 to 1 mmHg or about 200 to 3 mmHg. Herein, atemperature of the product may be controlled to be equal to that of theesterification or transesterification reaction or that of thepolycondensation reaction, or a temperature therebetween.

It is suitable that an intrinsic viscosity of the polymer obtained afterthe polycondensation reaction is 0.30 to 1.0 dVg. When the intrinsicviscosity is less than 0.30 dVg, a reaction rate of the solid-phasereaction may be significantly lowered. When the intrinsic viscosityexceeds 1.0 dVg, a viscosity of a molten material may be increasedduring the melt polymerization, and thus a possibility of polymerdiscoloration may be increased by shear stress between a stirrer and thereactor, resulting in by-products such as acetaldehyde.

The polyester resin according to the embodiment may have a higher degreeof polymerization by further performing a solid-phase reaction after thepolycondensation reaction, if necessary.

Specifically, the polymer obtained by the polycondensation reaction isdischarged out of the reactor to perform granulation. The granulationmay be performed by a strand cutting method in which the polymer isextruded into a strand shape, solidified in a cooling liquid, and cutwith a cutter, or an underwater cutting method in which a die hole isimmersed in a cooling liquid, the polymer is directly extruded into thecooling liquid and cut with a cutter. In general, a temperature of thecooling liquid should be kept low in the strand cutting method tosolidify the strand well, so that there is no problem in cutting. In theunderwater cutting method, it is preferable to maintain the temperatureof the cooling liquid in accordance with the polymer to make the shapeof the polymer uniform. However, in the case of a crystalline polymer,the temperature of the cooling liquid may be intentionally kept high inorder to induce crystallization during the discharge.

It is possible to remove raw materials soluble in water among unreactedraw materials such as isosorbide by water-washing the granulatedpolymer. The smaller the particle size, the wider the surface arearelative to a weight of particles. Accordingly, it is advantageous thata particle size is small. In order to achieve this purpose, theparticles may be made to have an average weight of about 15 mg or less.For example, the granulated polymer may be water-washed by leaving it inwater at a temperature equal to the glass transition temperature of thepolymer or lower than that by about 5 to 20° C. for 5 minutes to 10hours.

The granulated polymer is subjected to a crystallization step to preventfusion during the solid-phase reaction. The crystallization step may beperformed under an atmosphere, inert gas, water vapor, or watervapor-containing inert gas or in solution, and may be performed at 110to 210° C. or 120 to 210° C. When the temperature is low, a rate atwhich crystals of the particles are formed may be excessively slow. Whenthe temperature is high, a rate at which a surface of the particles ismelted may be faster than a rate at which the crystals are formed, sothat the particles may adhere to each other to cause fusion. Since theheat resistance of the particles is increased as the particles arecrystallized, it is also possible to crystallize the particles bydividing the crystallization into several steps and raising thetemperature stepwise.

The solid-phase reaction may be performed under an inert gas atmospheresuch as nitrogen, carbon dioxide, argon, and the like or under a reducedpressure of 400 to 0.01 mmHg and at a temperature of 180 to 220° C. foran average residence time of 1 to 150 hours. By performing thesolid-phase reaction, the molecular weight may be additionallyincreased, and the raw materials that do not react in the meltingreaction but just remain, and a cyclic oligomer, acetaldehyde, and thelike that are generated during the reaction may be removed.

The solid-phase reaction may be performed until the intrinsic viscosityof the crystallized polymer reaches 0.65 dVg or more, 0.70 dVg or more,0.75 dVg or more, or 0.80 dVg or more, wherein the intrinsic viscosityis measured at 35° C. after dissolving the polymer at a concentration of1.2 g/dl in orthochlorophenol at 150° C. for 15 minutes.

Meanwhile, the polyester resin blend may provide a molded article havingno flow-mark on the surface without special additives, even if itcontains up to about 50 wt % of recycled polyethylene terephthalate aspolyethylene terephthalate. Accordingly, the mixing ratio of thepolyethylene terephthalate and the polyester resin in the polyesterresin blend is not particularly limited.

For example, the polyester resin blend may include the polyethyleneterephthalate and the polyester resin in a weight ratio of 1:99 to 99:1,5:95 to 95:5, 10:90 to 90:10, 20:80 to 80:20, 30:70 to 70:30, 40:60 to60:40 or 50:50.

Meanwhile, the polyester resin blend according to the embodiment mayhave a melting temperature of 225 to 250° C., 230 to 245° C., or 235 to245° C. The polyester resin blend exhibits a melting temperature in theabove-described range, even if it includes recycled polyethyleneterephthalate, and thus can be reproduced as a molded article withexcellent quality.

Meanwhile, the polyester resin blend may have a haze of 5% or less, 4.5%or less, 4% or less, 3.5% or less, 3% or less, 2.5% or less, 2% or less,or 1% or less when measured for a 6 mm thick specimen according to ASTMD1003-97, indicating high transparency. As the haze is most preferably0% in theory, the lower limit may be 0% or more.

Even if the polyester resin blend according to the embodiment includesrecycled polyethylene terephthalate, miscibility of the polyester resinwith the recycled polyethylene terephthalate is excellent, and thusthere is an advantage that no additive is required to supplementproperties of the recycled polyethylene terephthalate. However, as anon-limiting example, the polyester resin blend may include an additivecommonly applied in the art.

In addition, the polyester resin blend is capable of providing a thickcontainer with high transparency even if it includes recycledpolyethylene terephthalate as well as virgin polyethylene terephthalate.Further, the resin blend can be reused by itself, and thus is expectedto be useful in providing a continuously usable plastic that has beenrecently attracting attention.

Hereinafter, action and effects of the present disclosure are describedby specific Examples in more detail. Meanwhile, these Examples areprovided by way of example, and therefore, should not be construed aslimiting the scope of the present invention.

The following physical properties were measured according to thefollowing methods.

(1) Intrinsic Viscosity (IV)

After dissolving a sample in o-chlorophenol at 150° C. for 15 minutes ata concentration of 1.2 g/dl, the intrinsic viscosity of the sample wasmeasured using an Ubbelohde viscometer. Specifically, a temperature ofthe viscometer was maintained at 35° C., and the time taken (effluxtime; to) for a solvent to pass between certain internal sections of theviscometer and the time taken (t) for a solution to pass the viscometerwere measured. Subsequently, a specific viscosity was calculated bysubstituting to and t into Formula 1, and the intrinsic viscosity wascalculated by substituting the calculated specific viscosity intoFormula 2.

$\begin{matrix}{\eta_{sp} = \frac{t - t_{0}}{t_{0}}} & \left\lbrack {{Formula}\mspace{14mu} 1} \right\rbrack \\{\lbrack\eta\rbrack = \frac{\sqrt{1 + {4A\eta_{s\rho}}} - 1}{2Ac}} & \left\lbrack {{Formula}\mspace{14mu} 2} \right\rbrack\end{matrix}$

In Formula 2, A was a Huggins constant of 0.247, and c was aconcentration of 0.12 wt %.

(2) Melting Temperature after Crystallization (Tm)

After crystallizing the polyester resin at 180° C. for 100 minutes, theTm of the crystallized sample was measured by differential scanningcalorimetry (DSC). DSC 1 model manufactured by Mettler Toledo was usedas a measuring device. Specifically, the crystallized sample was driedfor 5 to 10 hours under a nitrogen atmosphere at 120° C. using adehumidifying dryer (D2T manufactured by Moretto). Therefore, themelting temperature was measured in a state in which a moisture contentremaining in the sample was less than 500 ppm.

About 6 to 10 mg of the dried sample was taken, filled in an aluminumpan, maintained at a temperature of 30° C. for 3 minutes, heated at arate of 10° C./min from 30° C. to 280° C., and maintained at atemperature of 280° C. for 3 minutes (1st scan). Then, the Tm peak valuewas analyzed in the first scan by DSC using an integration function inTA menu of the related program (STARe software) provided by MettlerToledo. The temperature range of the first scan was set from onset point−10° C. to Tm peak +10° C., which was calculated by the program.

(3) Haze

A specimen having a thickness of 6 mm was prepared using a polyesterresin or a polyester resin blend, and the haze of the specimen wasmeasured using CM-3600A manufactured by Minolta according to ASTMD1003-97.

(4) Crystallization Half-Time

The crystallization half-time of the polyester resin was measured bydifferential scanning calorimetry (DSC). Specifically, after thepolyester resin was completely melted, the temperature was maintained ata crystallized temperature, and the time (unit: minute) consumed togenerate half of the total heat generated during crystallization wasmeasured.

(5) Molecular Weight

The molecular weight of the polyester resin was measured by GPC (GelPermeation Chromatography). Specifically, 0.03 g of a polyester resinwas added to 3 mL of o-chlorophenol, and dissolved at 150° C. for 15minutes. Then, 9 mL of chloroform was added thereto to prepare a sample,while cooling to room temperature. Then, two columns (Shodex LF804) wereused to conduct gel permeation chromatography on the sample at a flowrate of 0.7 mL/min at a temperature of 40° C. The number averagemolecular weight (Mn) was calculated using polystyrene as a standardmaterial.

(6) 2nd Melting Temperature

The second melting temperature of the polyester resin blend was measuredby differential scanning calorimetry (DSC). DSC 1 model manufactured byMettler Toledo was used as a measuring device. Specifically, thepolyester resin blend was dried for 5 to 10 hours under a nitrogenatmosphere at 120° C. using a dehumidifying dryer (D2T manufactured byMoretto). Therefore, the melting temperature was measured in a state inwhich a moisture content remaining in the sample was less than 500 ppm.

About 6 to 10 mg of the dried sample was taken, filled in an aluminumpan, maintained at a temperature of 30° C. for 3 minutes, heated at arate of 10° C./min from 30° C. to 280° C., and maintained at atemperature of 280° C. for 3 minutes (1st scan). After the first scan,the sample was rapidly cooled to room temperature, and then heated at arate of 10° C./min from room temperature to 280° C. (2nd scan) to obtaina DSC curve. Then, the Tm peak value was analyzed in the second scan byDSC using an integration function in TA menu of the related program(STARe software) provided by Mettler Toledo. The temperature range ofthe second scan was set from onset point −10° C. to Tm peak +10° C.,which was calculated by the program.

(7) Occurrence of Flow-Mark

36 g of preform was prepared by injection-molding a polyester resinblend. Thereafter, the preform was reheated to about 140° C., and thenblow-molded to prepare a 500 mL bottle. During the blow molding, thetemperature of the mold was adjusted to about 70° C. The prepared 500 mLbottle was visually observed to indicate ‘O’ when flow-mark wasobserved, and ‘X’ when not observed.

(8) Occurrence of Flake Fusion During Recycling

The bottle evaluated for the occurrence of flow-mark in (7) waspulverized to obtain flakes having a bulk density of about 250 to 600g/L. The obtained flakes were left at 220° C. for 1 hour to visuallyobserve whether or not the flakes were fused. When some fused parts wereobserved, it was indicated as ‘O’, and when not observed, it wasindicated as ‘X’.

(9) Loss Modulus Onset Point

The Young's modulus or storage modulus (E′) and the loss modulus (E″) ofthe polyester resin blend were measured by dynamic mechanical analysis(DMA), and the crystallization rate of the polyester resin blend wasevaluated based thereon.

Specifically, the polyester resin blend was extruded into a sheet form,cut to a size of 30 mm×5.3 mm (longitudinal length×transverse length),and then E′ and E″ were measured under the following conditions usingDMA. Then, the loss modulus onset point was determined as a point intime at which crystallization of the polyester resin blend began.

<Measuring Conditions>

Frequency fixed (Frequency sweep/Amplitude: 15 μm)

Temperature change: temperature increases at a rate of 3° C./min fromroom temperature up to 150° C.

When the loss modulus onset point is high, the polyester resineffectively slows down the high crystallization rate of recycled PET,which is advantageous for the production of a thick container with hightransparency.

Preparation Example 1: Preparation of Polyester Resin

3257.4 g (19.6 mol) of terephthalic acid, 1423.4 g (23.0 mol) ofethylene glycol, and 229.2 g (1.6 mol) of isosorbide were placed in a 10L reactor to which a column, and a condenser capable of being cooled bywater were connected, and 1.0 g of GeO₂ as a catalyst, 1.46 g ofphosphoric acid as a stabilizer, and 0.7 g of cobalt acetate as acoloring agent were used. Then, nitrogen was injected into the reactorto form a pressurized state in which the pressure of the reactor washigher than normal pressure by 1.0 kgf/cm² (absolute pressure: 1495.6mmHg).

Then, the temperature of the reactor was raised to 220° C. over 90minutes, maintained at 220° C. for 2 hours, and then raised to 260° C.over 2 hours. Thereafter, an esterification reaction proceeded until themixture in the reactor became transparent with the naked eye whilemaintaining the temperature of the reactor at 260° C. When theesterification reaction was completed, the nitrogen in the pressurizedreactor was discharged to the outside to lower the pressure of thereactor to normal pressure, and then the mixture in the reactor wastransferred to a 7 L reactor capable of vacuum reaction.

Then, the pressure of the reactor was reduced from normal pressure to 5Torr (absolute pressure: 5 mmHg) over 30 minutes, and the temperature ofthe reactor was raised to 280° C. over 1 hour to proceed apolycondensation reaction while maintaining the pressure of the reactorat 1 Torr (absolute pressure: 1 mmHg) or less. In the initial stage ofthe polycondensation reaction, a stirring rate was set high, but whenthe stirring force is weakened due to an increase in the viscosity ofthe reactant as the polycondensation reaction progresses or thetemperature of the reactant rises above the set temperature, thestirring rate may be appropriately adjusted. The polycondensationreaction was performed until an intrinsic viscosity (IV) of the mixture(melt) in the reactor became 0.55 dVg. When the intrinsic viscosity ofthe mixture in the reactor reached a desired level, the mixture wasdischarged out of the reactor and stranded. This was solidified with acooling liquid and granulated to have an average weight of about 12 to14 mg.

The particles were allowed to stand at 150° C. for 1 hour tocrystallize, and then put into a 20 L solid-phase polymerizationreactor. Then, nitrogen was flowed into the reactor at a rate of 50L/min. Herein, the temperature of the reactor was raised from roomtemperature to 140° C. at a rate of 40° C./hour, and maintained at 140°C. for 3 hours. Thereafter, the temperature was further raised to 200°C. at a rate of 40° C./hour, and maintained at 200° C. The solid-phasepolymerization reaction was performed until the intrinsic viscosity ofthe particles in the reactor reached 0.70 dVg.

A content of a residue derived from isosorbide with respect to the totalresidue derived from a diol contained in the polyester resin was 5 mol%.

Preparation Example 2: Preparation of First Polyester Resin

3189.1 g (19.2 mol) of terephthalic acid, 1334.1 g (21.5 mol) ofethylene glycol, and 504.9 g (3.5 mol) of isosorbide were placed in a 10L reactor to which a column, and a condenser capable of being cooled bywater were connected, and 1.0 g of GeO₂ as a catalyst, 1.46 g ofphosphoric acid as a stabilizer, and 0.7 g of cobalt acetate as acoloring agent were used. Then, nitrogen was injected into the reactorto form a pressurized state in which the pressure of the reactor washigher than normal pressure by 1.0 kgf/cm² (absolute pressure: 1495.6mmHg).

Then, the temperature of the reactor was raised to 220° C. over 90minutes, maintained at 220° C. for 2 hours, and then raised to 260° C.over 2 hours. Thereafter, an esterification reaction proceeded until themixture in the reactor became transparent with the naked eye whilemaintaining the temperature of the reactor at 260° C. When theesterification reaction was completed, the nitrogen in the pressurizedreactor was discharged to the outside to lower the pressure of thereactor to normal pressure, and then the mixture in the reactor wastransferred to a 7 L reactor capable of vacuum reaction.

Then, the pressure of the reactor was reduced from normal pressure to 5Torr (absolute pressure: 5 mmHg) over 30 minutes, and the temperature ofthe reactor was raised to 280° C. over 1 hour to proceed apolycondensation reaction while maintaining the pressure of the reactorat 1 Torr (absolute pressure: 1 mmHg) or less. In the initial stage ofthe polycondensation reaction, a stirring rate was set high, but whenthe stirring force is weakened due to an increase in the viscosity ofthe reactant as the polycondensation reaction progresses or thetemperature of the reactant rises above the set temperature, thestirring rate may be appropriately adjusted. The polycondensationreaction was performed until an intrinsic viscosity (IV) of the mixture(melt) in the reactor became 0.50 dVg. When the intrinsic viscosity ofthe mixture in the reactor reached a desired level, the mixture wasdischarged out of the reactor and stranded. This was solidified with acooling liquid and granulated to have an average weight of about 12 to14 mg. The particles thus obtained were stored in water at 70° C. for 5hours to remove unreacted raw materials contained in the particles.

The particles were allowed to stand at 150° C. for 1 hour tocrystallize, and then put into a 20 L solid-phase polymerizationreactor. Then, nitrogen was flowed into the reactor at a rate of 50L/min. Herein, the temperature of the reactor was raised from roomtemperature to 140° C. at a rate of 40° C./hour, and maintained at 140°C. for 3 hours. Thereafter, the temperature was further raised to 200°C. at a rate of 40° C./hour, and maintained at 200° C. The solid-phasepolymerization reaction was performed until the intrinsic viscosity ofthe particles in the reactor reached 0.95 dVg.

A content of a residue derived from isosorbide with respect to the totalresidue derived from a diol contained in the polyester resin was 10 mol%.

Preparation Example 3: Preparation of Third Polyester Resin

3356.5 g (20.2 mol) of terephthalic acid, 1341.4 g (21.6 mol) ofethylene glycol, and 826.6 g (5.7 mol) of isosorbide were placed in a 10L reactor to which a column, and a condenser capable of being cooled bywater were connected, and 1.0 g of GeO₂ as a catalyst, 1.46 g ofphosphoric acid as a stabilizer, 0.016 g of Clarient's Polysynthren BlueRLS as a blue toner, 0.004 g of Clarient's Solvaperm Red BB as a redtoner, 1 ppm of polyethylene as a crystallization agent, and 1000 ppm ofIrganox 1076 as an antioxidant were used. Then, nitrogen was injectedinto the reactor to form a pressurized state in which the pressure ofthe reactor was higher than normal pressure by 0.5 kgf/cm² (absolutepressure: 1127.8 mmHg).

Then, the temperature of the reactor was raised to 220° C. over 90minutes, maintained at 220° C. for 2 hours, and then raised to 260° C.over 2 hours. Thereafter, an esterification reaction proceeded until themixture in the reactor became transparent with the naked eye whilemaintaining the temperature of the reactor at 260° C. When theesterification reaction was completed, the nitrogen in the pressurizedreactor was discharged to the outside to lower the pressure of thereactor to normal pressure, and then the mixture in the reactor wastransferred to a 7 L reactor capable of vacuum reaction.

Then, the pressure of the reactor was reduced from normal pressure to 5Torr (absolute pressure: 5 mmHg) over 30 minutes, and the temperature ofthe reactor was raised to 275° C. over 1 hour to proceed apolycondensation reaction while maintaining the pressure of the reactorat 1 Torr (absolute pressure: 1 mmHg) or less. In the initial stage ofthe polycondensation reaction, a stirring rate was set high, but whenthe stirring force is weakened due to an increase in the viscosity ofthe reactant as the polycondensation reaction progresses or thetemperature of the reactant rises above the set temperature, thestirring rate may be appropriately adjusted. The polycondensationreaction was performed until an intrinsic viscosity (IV) of the mixture(melt) in the reactor became 0.60 dVg.

A content of a residue derived from isosorbide with respect to the totalresidue derived from a diol contained in the polyester resin was 14 mol%.

Preparation Example 4: Preparation of First Polyester Resin

4297.3 g (25.9 mol) of terephthalic acid, 1845.8 g (29.8 mol) ofethylene glycol, 189.0 g (1.3 mol) of isosorbide, and 186.4 g (1.3 mol)of 1,4-cyclohexanedimethanol were placed in a 10 L reactor to which acolumn, and a condenser capable of being cooled by water were connected,and 1.0 g of GeO₂ as a catalyst, 1.46 g of phosphoric acid as astabilizer, 1.1 g of cobalt acetate as a coloring agent, and 1000 ppm oftrimellitic anhydrate as a branching agent were used. Then, nitrogen wasinjected into the reactor to form a pressurized state in which thepressure of the reactor was higher than normal pressure by 1.0 kgf/cm²(absolute pressure: 1495.6 mmHg).

Then, the temperature of the reactor was raised to 220° C. over 90minutes, maintained at 220° C. for 2 hours, and then raised to 250° C.over 2 hours. Thereafter, the temperature of the reactor was maintainedat 250° C. until the mixture in the reactor became transparent with thenaked eye. When the esterification reaction was completed, the nitrogenin the pressurized reactor was discharged to the outside to lower thepressure of the reactor to normal pressure, and then the mixture in thereactor was transferred to a 7 L reactor capable of vacuum reaction.

Then, the pressure of the reactor was reduced from normal pressure to 5Torr (absolute pressure: 5 mmHg) over 30 minutes, and the temperature ofthe reactor was raised to 265° C. over 1 hour to proceed apolycondensation reaction while maintaining the pressure of the reactorat 1 Torr (absolute pressure: 1 mmHg) or less. In the initial stage ofthe polycondensation reaction, a stirring rate was set high, but whenthe stirring force is weakened due to an increase in the viscosity ofthe reactant as the polycondensation reaction progresses or thetemperature of the reactant rises above the set temperature, thestirring rate may be appropriately adjusted. The polycondensationreaction was performed until an intrinsic viscosity (IV) of the mixture(melt) in the reactor became 0.60 dVg.

A content of a residue derived from isosorbide was 2 mol % and a contentof a residue derived from 1,4-cyclohexanedimethanol was 5 mol % withrespect to the total residue derived from a diol contained in thepolyester resin.

Preparation Example 5: Preparation of Fourth Polyester Resin

3316.0 g (20.0 mol) of terephthalic acid, 1164.2 g (18.8 mol) ofethylene glycol, 87.5 g (0.6 mol) of isosorbide, and 230.1 g (1.6 mol)of 1,4-cyclohexanedimethanol were placed in a 10 L reactor to which acolumn, and a condenser capable of being cooled by water were connected,and 1.0 g of GeO₂ as a catalyst, 1.46 g of phosphoric acid as astabilizer, and 0.8 g of cobalt acetate as a coloring agent were used.Then, nitrogen was injected into the reactor to form a pressurized statein which the pressure of the reactor was higher than normal pressure by2.0 kgf/cm² (absolute pressure: 2231.1 mmHg).

Then, the temperature of the reactor was raised to 220° C. over 90minutes, maintained at 220° C. for 2 hours, and then raised to 255° C.over 2 hours. Thereafter, the temperature of the reactor was maintainedat 255° C. until the mixture in the reactor became transparent with thenaked eye. When the esterification reaction was completed, the nitrogenin the pressurized reactor was discharged to the outside to lower thepressure of the reactor to normal pressure, and then the mixture in thereactor was transferred to a 7 L reactor capable of vacuum reaction.

Then, the pressure of the reactor was reduced from normal pressure to 5Torr (absolute pressure: 5 mmHg) over 30 minutes, and the temperature ofthe reactor was raised to 285° C. over 1 hour to proceed apolycondensation reaction while maintaining the pressure of the reactorat 1 Torr (absolute pressure: 1 mmHg) or less. In the initial stage ofthe polycondensation reaction, a stirring rate was set high, but whenthe stirring force is weakened due to an increase in the viscosity ofthe reactant as the polycondensation reaction progresses or thetemperature of the reactant rises above the set temperature, thestirring rate may be appropriately adjusted. The polycondensationreaction was performed until an intrinsic viscosity (IV) of the mixture(melt) in the reactor became 0.55 dVg.

A content of a residue derived from isosorbide was 2 mol % and a contentof a residue derived from 1,4-cyclohexanedimethanol was 8 mol % withrespect to the total residue derived from a diol contained in thepolyester resin.

Preparation Example 6: Preparation of Third Polyester Resin

3124.0 g (18.8 mol) of terephthalic acid, 1330.2 g (21.5 mol) ofethylene glycol, 219.8 g (1.5 mol) of isosorbide, and 216.8 g (1.5 mol)of 1,4-cyclohexanedimethanol were placed in a 10 L reactor to which acolumn, and a condenser capable of being cooled by water were connected,and 1.0 g of GeO₂ as a catalyst, 1.46 g of phosphoric acid as astabilizer, 1.0 g of cobalt acetate as a coloring agent and 1000 ppm ofIrganox 1076 as an antioxidant were used. Then, nitrogen was injectedinto the reactor to form a pressurized state in which the pressure ofthe reactor was higher than normal pressure by 1.5 kgf/cm² (absolutepressure: 1863.3 mmHg).

Then, the temperature of the reactor was raised to 220° C. over 90minutes, maintained at 220° C. for 2 hours, and then raised to 250° C.over 2 hours. Thereafter, an esterification reaction proceeded until themixture in the reactor became transparent with the naked eye whilemaintaining the temperature of the reactor at 250° C. When theesterification reaction was completed, the nitrogen in the pressurizedreactor was discharged to the outside to lower the pressure of thereactor to normal pressure, and then the mixture in the reactor wastransferred to a 7 L reactor capable of vacuum reaction.

Then, the pressure of the reactor was reduced from normal pressure to 5Torr (absolute pressure: 5 mmHg) over 30 minutes, and the temperature ofthe reactor was raised to 270° C. over 1 hour to proceed apolycondensation reaction while maintaining the pressure of the reactorat 1 Torr (absolute pressure: 1 mmHg) or less. In the initial stage ofthe polycondensation reaction, a stirring rate was set high, but whenthe stirring force is weakened due to an increase in the viscosity ofthe reactant as the polycondensation reaction progresses or thetemperature of the reactant rises above the set temperature, thestirring rate may be appropriately adjusted. The polycondensationreaction was performed until an intrinsic viscosity (IV) of the mixture(melt) in the reactor became 0.60 dVg. When the intrinsic viscosity ofthe mixture in the reactor reached a desired level, the mixture wasdischarged out of the reactor and stranded. This was solidified with acooling liquid and granulated to have an average weight of about 12 to14 mg.

The particles were allowed to stand at 150° C. for 1 hour tocrystallize, and then put into a 20 L solid-phase polymerizationreactor. Then, nitrogen was flowed into the reactor at a rate of 50L/min. Herein, the temperature of the reactor was raised from roomtemperature to 140° C. at a rate of 40° C./hour, and maintained at 140°C. for 3 hours. Thereafter, the temperature was further raised to 200°C. at a rate of 40° C./hour, and maintained at 200° C. The solid-phasepolymerization reaction was performed until the intrinsic viscosity ofthe particles in the reactor reached 0.75 dVg.

A content of a residue derived from isosorbide was 4 mol % and a contentof a residue derived from 1,4-cyclohexanedimethanol was 8 mol % withrespect to the total residue derived from a diol contained in thepolyester resin.

Preparation Example 7: Preparation of Fourth Polyester Resin

3371.0 g (20.3 mol) of terephthalic acid, 1435.3 g (23.2 mol) ofethylene glycol, 177.9 g (1.2 mol) of isosorbide, and 438.6 g (3.0 mol)of 1,4-cyclohexanedimethanol were placed in a 10 L reactor to which acolumn, and 1.0 g of GeO₂ as a catalyst, 1.46 g of phosphoric acid as astabilizer, 0.013 g of Clarient's Polysynthren Blue RLS as a blue toner,and 0.004 g of Clarient's Solvaperm Red BB as a red toner were used.Then, nitrogen was injected into the reactor to form a pressurized statein which the pressure of the reactor was higher than normal pressure by1.0 kgf/cm² (absolute pressure: 1495.6 mmHg).

Then, the temperature of the reactor was raised to 220° C. over 90minutes, maintained at 220° C. for 2 hours, and then raised to 265° C.over 2 hours. Thereafter, an esterification reaction proceeded until themixture in the reactor became transparent with the naked eye whilemaintaining the temperature of the reactor at 265° C. When theesterification reaction was completed, the nitrogen in the pressurizedreactor was discharged to the outside to lower the pressure of thereactor to normal pressure, and then the mixture in the reactor wastransferred to a 7 L reactor capable of vacuum reaction.

Then, the pressure of the reactor was reduced from normal pressure to 5Torr (absolute pressure: 5 mmHg) over 30 minutes, and the temperature ofthe reactor was raised to 275° C. over 1 hour to proceed apolycondensation reaction while maintaining the pressure of the reactorat 1 Torr (absolute pressure: 1 mmHg) or less. In the initial stage ofthe polycondensation reaction, a stirring rate was set high, but whenthe stirring force is weakened due to an increase in the viscosity ofthe reactant as the polycondensation reaction progresses or thetemperature of the reactant rises above the set temperature, thestirring rate may be appropriately adjusted. The polycondensationreaction was performed until an intrinsic viscosity (IV) of the mixture(melt) in the reactor became 0.70 dVg.

A content of a residue derived from isosorbide was 3 mol % and a contentof a residue derived from 1,4-cyclohexanedimethanol was 15 mol % withrespect to the total residue derived from a diol contained in thepolyester resin.

Preparation Example 8: Preparation of Fourth Polyester Resin

3727.0 g (19.2 mol) of dimethyl terephthalate, 2620.5 g (42.3 mol) ofethylene glycol, and 841.5 g (5.8 mol) of isosorbide were placed in a 10L reactor to which a column, and a condenser capable of being cooled bywater were connected, and 1.5 g of Mn(II) acetate tetrahydrate and 1.8 gof Sb₂O₃ as a catalyst, and 0.7 g of cobalt acetate as a coloring agentwere used. Then, nitrogen was injected into the reactor, but thepressure of the reactor was not increased (absolute pressure: 760 mmHg).

Then, the temperature of the reactor was raised to 220° C. over 90minutes, maintained at 220° C. for 2 hours, and then raised to 240° C.over 2 hours. Thereafter, a transesterification reaction proceeded untilthe mixture in the reactor became transparent with the naked eye whilemaintaining the temperature of the reactor at 240° C. When thetransesterification reaction was completed, the mixture in the reactorwas transferred to a 7 L reactor capable of vacuum reaction.

Then, the pressure of the reactor was reduced from normal pressure to 5Torr (absolute pressure: 5 mmHg) over 30 minutes, and the temperature ofthe reactor was raised to 265° C. over 1 hour to proceed apolycondensation reaction while maintaining the pressure of the reactorat 1 Torr (absolute pressure: 1 mmHg) or less. In the initial stage ofthe polycondensation reaction, a stirring rate was set high, but whenthe stirring force is weakened due to an increase in the viscosity ofthe reactant as the polycondensation reaction progresses or thetemperature of the reactant rises above the set temperature, thestirring rate may be appropriately adjusted. The polycondensationreaction was performed until an intrinsic viscosity (IV) of the mixture(melt) in the reactor became 0.50 dVg. When the intrinsic viscosity ofthe mixture in the reactor reached a desired level, the mixture wasdischarged out of the reactor and stranded. This was solidified with acooling liquid and granulated to have an average weight of about 12 to14 mg.

The particles were allowed to stand at 160° C. for 1 hour tocrystallize, and then put into a 20 L solid-phase polymerizationreactor. Then, nitrogen was flowed into the reactor at a rate of 50L/min. Herein, the temperature of the reactor was raised from roomtemperature to 140° C. at a rate of 40° C./hour, and maintained at 140°C. for 3 hours. Thereafter, the temperature was further raised to 200°C. at a rate of 40° C./hour, and maintained at 200° C. The solid-phasepolymerization reaction was performed until the intrinsic viscosity ofthe particles in the reactor reached 0.95 dVg.

A content of a residue derived from isosorbide with respect to the totalresidue derived from a diol contained in the polyester resin was 10 mol%.

Preparation Example 9: Preparation of First Polyester Resin

3029.7 g (18.3 mol) of terephthalic acid, 159.5 g (0.96 mol) ofisophthalic acid, 1334.1 g (21.5 mol) of ethylene glycol, and 504.9 g(3.5 mol) of isosorbide were placed in a 10 L reactor to which a column,and a condenser capable of being cooled by water were connected, and 1.0g of GeO₂ as a catalyst, 1.46 g of phosphoric acid as a stabilizer, and0.7 g of cobalt acetate as a coloring agent were used. Then, nitrogenwas injected into the reactor to form a pressurized state in which thepressure of the reactor was higher than normal pressure by 1.0 kgf/cm²(absolute pressure: 1495.6 mmHg).

Then, the temperature of the reactor was raised to 220° C. over 90minutes, maintained at 220° C. for 2 hours, and then raised to 260° C.over 2 hours. Thereafter, an esterification reaction proceeded until themixture in the reactor became transparent with the naked eye whilemaintaining the temperature of the reactor at 260° C. When theesterification reaction was completed, the nitrogen in the pressurizedreactor was discharged to the outside to lower the pressure of thereactor to normal pressure, and then the mixture in the reactor wastransferred to a 7 L reactor capable of vacuum reaction.

Then, the pressure of the reactor was reduced from normal pressure to 5Torr (absolute pressure: 5 mmHg) over 30 minutes, and the temperature ofthe reactor was raised to 280° C. over 1 hour to proceed apolycondensation reaction while maintaining the pressure of the reactorat 1 Torr (absolute pressure: 1 mmHg) or less. In the initial stage ofthe polycondensation reaction, a stirring rate was set high, but whenthe stirring force is weakened due to an increase in the viscosity ofthe reactant as the polycondensation reaction progresses or thetemperature of the reactant rises above the set temperature, thestirring rate may be appropriately adjusted. The polycondensationreaction was performed until an intrinsic viscosity (IV) of the mixture(melt) in the reactor became 0.50 dVg. When the intrinsic viscosity ofthe mixture in the reactor reached a desired level, the mixture wasdischarged out of the reactor and stranded. This was solidified with acooling liquid and granulated to have an average weight of about 12 to14 mg.

The particles were allowed to stand at 150° C. for 1 hour tocrystallize, and then put into a 20 L solid-phase polymerizationreactor. Then, nitrogen was flowed into the reactor at a rate of 50L/min. Herein, the temperature of the reactor was raised from roomtemperature to 140° C. at a rate of 40° C./hour, and maintained at 140°C. for 3 hours. Thereafter, the temperature was further raised to 200°C. at a rate of 40° C./hour, and maintained at 200° C. The solid-phasepolymerization reaction was performed until the intrinsic viscosity ofthe particles in the reactor reached 0.95 dVg.

A content of a residue derived from terephthalic acid was 95 mol % and acontent of a residue derived from isophthalic acid was 5 mol % withrespect to the total residue derived from an acid contained in thepolyester resin, and a content of a residue derived from isosorbide withrespect to the total residue derived from a diol was 10 mol %.

Comparative Preparation Example 1: Preparation of Third Polyester Resin

3000.5 g (18.1 mol) of terephthalic acid, 1064.6 g (17.2 mol) ofethylene glycol, and 1187.5 g (8.1 mol) of isosorbide were placed in a10 L reactor to which a column, and a condenser capable of being cooledby water were connected, and 1.0 g of GeO₂ as a catalyst, 1.46 g ofphosphoric acid as a stabilizer, 0.017 g of Clarient's Polysynthren BlueRLS as a blue toner, and 0.006 g of Clarient's Solvaperm Red BB as a redtoner were used. Then, nitrogen was injected into the reactor to form apressurized state in which the pressure of the reactor was higher thannormal pressure by 0.5 kgf/cm² (absolute pressure: 1127.8 mmHg).

Then, the temperature of the reactor was raised to 220° C. over 90minutes, maintained at 220° C. for 2 hours, and then raised to 260° C.over 2 hours. Thereafter, an esterification reaction proceeded until themixture in the reactor became transparent with the naked eye whilemaintaining the temperature of the reactor at 260° C. When theesterification reaction was completed, the nitrogen in the pressurizedreactor was discharged to the outside to lower the pressure of thereactor to normal pressure, and then the mixture in the reactor wastransferred to a 7 L reactor capable of vacuum reaction.

Then, the pressure of the reactor was reduced from normal pressure to100 Torr (absolute pressure: 100 mmHg) over 10 minutes, and thispressure was maintained for 1 hour. Thereafter, the temperature of thereactor was raised to 280° C. over 1 hour to proceed a polycondensationreaction while maintaining the pressure of the reactor at 1 Torr(absolute pressure: 1 mmHg) or less. In the initial stage of thepolycondensation reaction, a stirring rate was set high, but when thestirring force is weakened due to an increase in the viscosity of thereactant as the polycondensation reaction progresses or the temperatureof the reactant rises above the set temperature, the stirring rate maybe appropriately adjusted. The polycondensation reaction was performeduntil an intrinsic viscosity (IV) of the mixture (melt) in the reactorbecame 0.60 dVg.

A content of a residue derived from isosorbide with respect to the totalresidue derived from a diol contained in the polyester resin was 25 mol%.

Comparative Preparation Example 2: Preparation of Third Polyester Resin

2518.5 g (15.2 mol) of terephthalic acid, 1044.1 g (16.8 mol) ofethylene glycol, 398.7 g (2.7 mol) of isosorbide and 240.3 g (1.7 mol)of 1,4-cyclohexanedimethanol were placed in a 10 L reactor to which acolumn, and a condenser capable of being cooled by water were connected,and 1.0 g of GeO₂ as a catalyst, 1.46 g of phosphoric acid as astabilizer, 0.010 g of Clarient's Polysynthren Blue RLS as a blue toner,and 0.003 g of Clarient's Solvaperm Red BB as a red toner were used.Then, nitrogen was injected into the reactor to form a pressurized statein which the pressure of the reactor was higher than normal pressure by1.5 kgf/cm² (absolute pressure: 1863.3 mmHg).

Then, the temperature of the reactor was raised to 220° C. over 90minutes, maintained at 220° C. for 2 hours, and then raised to 260° C.over 2 hours. Thereafter, an esterification reaction proceeded until themixture in the reactor became transparent with the naked eye whilemaintaining the temperature of the reactor at 260° C. When theesterification reaction was completed, the nitrogen in the pressurizedreactor was discharged to the outside to lower the pressure of thereactor to normal pressure, and then the mixture in the reactor wastransferred to a 7 L reactor capable of vacuum reaction.

Then, the pressure of the reactor was reduced from normal pressure to 5Torr (absolute pressure: 5 mmHg) over 30 minutes, and the temperature ofthe reactor was raised to 270° C. over 1 hour to proceed apolycondensation reaction while maintaining the pressure of the reactorat 1 Torr (absolute pressure: 1 mmHg) or less. In the initial stage ofthe polycondensation reaction, a stirring rate was set high, but whenthe stirring force is weakened due to an increase in the viscosity ofthe reactant as the polycondensation reaction progresses or thetemperature of the reactant rises above the set temperature, thestirring rate may be appropriately adjusted. The polycondensationreaction was performed until an intrinsic viscosity (IV) of the mixture(melt) in the reactor became 0.65 dVg.

A content of a residue derived from isosorbide was 11 mol % and acontent of a residue derived from 1,4-cyclohexanedimethanol was 11 mol %with respect to the total residue derived from a diol contained in thepolyester resin.

Comparative Preparation Example 3: Preparation of Third Polyester Resin

3631.3 g (21.9 mol) of terephthalic acid, and 1763.1 g (28.4 mol) ofethylene glycol were placed in a 10 L reactor to which a column, and acondenser capable of being cooled by water were connected, and 1.0 g ofGeO₂ as a catalyst, 1.5 g of phosphoric acid as a stabilizer, 0.7 g ofcobalt acetate as a coloring agent and 1000 ppm of Irganox 1076 as anantioxidant were used. Then, nitrogen was injected into the reactor toform a pressurized state in which the pressure of the reactor was higherthan normal pressure by 2.0 kgf/cm² (absolute pressure: 2231.1 mmHg).

Then, the temperature of the reactor was raised to 220° C. over 90minutes, maintained at 220° C. for 2 hours, and then raised to 265° C.over 2 hours. Thereafter, an esterification reaction proceeded until themixture in the reactor became transparent with the naked eye whilemaintaining the temperature of the reactor at 265° C. When theesterification reaction was completed, the nitrogen in the pressurizedreactor was discharged to the outside to lower the pressure of thereactor to normal pressure, and then the mixture in the reactor wastransferred to a 7 L reactor capable of vacuum reaction.

Then, the pressure of the reactor was reduced from normal pressure to 5Torr (absolute pressure: 5 mmHg) over 30 minutes, and the temperature ofthe reactor was raised to 270° C. over 1 hour to proceed apolycondensation reaction while maintaining the pressure of the reactorat 1 Torr (absolute pressure: 1 mmHg) or less. In the initial stage ofthe polycondensation reaction, a stirring rate was set high, but whenthe stirring force is weakened due to an increase in the viscosity ofthe reactant as the polycondensation reaction progresses or thetemperature of the reactant rises above the set temperature, thestirring rate may be appropriately adjusted. The polycondensationreaction was performed until an intrinsic viscosity (IV) of the mixture(melt) in the reactor became 0.60 dVg. When the intrinsic viscosity ofthe mixture in the reactor reached a desired level, the mixture wasdischarged out of the reactor and stranded. This was solidified with acooling liquid and granulated to have an average weight of about 12 to14 mg.

The particles were allowed to stand at 150° C. for 1 hour tocrystallize, and then put into a 20 L solid-phase polymerizationreactor. Then, nitrogen was flowed into the reactor at a rate of 50L/min. Herein, the temperature of the reactor was raised from roomtemperature to 140° C. at a rate of 40° C./hour, and maintained at 140°C. for 3 hours. Thereafter, the temperature was further raised to 200°C. at a rate of 40° C./hour, and maintained at 200° C. The solid-phasepolymerization reaction was performed until the intrinsic viscosity ofthe particles in the reactor reached 0.75 dVg.

A content of a residue derived from isosorbide was 0 mol % and a contentof a residue derived from 1,4-cyclohexanedimethanol was 0 mol % withrespect to the total residue derived from a diol contained in thepolyester resin.

Comparative Preparation Example 4: Preparation of Third Polyester Resin

3328.2 g (20.0 mol) of terephthalic acid, 1479.2 g (23.9 mol) ofethylene glycol, and 175.6 g (1.2 mol) of isosorbide were placed in a 10L reactor to which a column, and a condenser capable of being cooled bywater were connected, and 1.0 g of GeO₂ as a catalyst, 1.46 g ofphosphoric acid as a stabilizer, 0.8 g of cobalt acetate as a coloringagent, and 1 ppm of polyethylene as a crystallization agent were used.Then, nitrogen was injected into the reactor to form a pressurized statein which the pressure of the reactor was higher than normal pressure by1.5 kgf/cm² (absolute pressure: 1863.3 mmHg).

Then, the temperature of the reactor was raised to 220° C. over 90minutes, maintained at 220° C. for 2 hours, and then raised to 270° C.over 2 hours. Thereafter, an esterification reaction proceeded until themixture in the reactor became transparent with the naked eye whilemaintaining the temperature of the reactor at 270° C. When theesterification reaction was completed, the nitrogen in the pressurizedreactor was discharged to the outside to lower the pressure of thereactor to normal pressure, and then the mixture in the reactor wastransferred to a 7 L reactor capable of vacuum reaction.

Then, the pressure of the reactor was reduced from normal pressure to 5Torr (absolute pressure: 5 mmHg) over 30 minutes, and the temperature ofthe reactor was raised to 275° C. over 1 hour to proceed apolycondensation reaction while maintaining the pressure of the reactorat 1 Torr (absolute pressure: 1 mmHg) or less. In the initial stage ofthe polycondensation reaction, a stirring rate was set high, but whenthe stirring force is weakened due to an increase in the viscosity ofthe reactant as the polycondensation reaction progresses or thetemperature of the reactant rises above the set temperature, thestirring rate may be appropriately adjusted. The polycondensationreaction was performed until an intrinsic viscosity (IV) of the mixture(melt) in the reactor became 0.65 dVg.

A content of a residue derived from isosorbide with respect to the totalresidue derived from a diol contained in the polyester resin was 3 mol%.

Comparative Preparation Example 5: Preparation of Third Polyester Resin

3247.1 g (19.6 mol) of terephthalic acid, 1406.8 g (22.7 mol) ofethylene glycol, and 253.5 g (1.8 mol) of 1,4-cyclohexanedimethanol wereplaced in a 10 L reactor to which a column, and a condenser capable ofbeing cooled by water were connected, and 1.0 g of GeO₂ as a catalyst,1.46 g of phosphoric acid as a stabilizer, and 0.8 g of cobalt acetateas a coloring agent were used. Then, nitrogen was injected into thereactor to form a pressurized state in which the pressure of the reactorwas higher than normal pressure by 1.0 kgf/cm² (absolute pressure:1495.6 mmHg).

Then, the temperature of the reactor was raised to 220° C. over 90minutes, maintained at 220° C. for 2 hours, and then raised to 260° C.over 2 hours. Thereafter, the temperature of the reactor was maintainedat 260° C. until the mixture in the reactor became transparent with thenaked eye. When the esterification reaction was completed, the nitrogenin the pressurized reactor was discharged to the outside to lower thepressure of the reactor to normal pressure, and then the mixture in thereactor was transferred to a 7 L reactor capable of vacuum reaction.

Then, the pressure of the reactor was reduced from normal pressure to 5Torr (absolute pressure: 5 mmHg) over 30 minutes, and the temperature ofthe reactor was raised to 280° C. over 1 hour to proceed apolycondensation reaction while maintaining the pressure of the reactorat 1 Torr (absolute pressure: 1 mmHg) or less. In the initial stage ofthe polycondensation reaction, a stirring rate was set high, but whenthe stirring force is weakened due to an increase in the viscosity ofthe reactant as the polycondensation reaction progresses or thetemperature of the reactant rises above the set temperature, thestirring rate may be appropriately adjusted. The polycondensationreaction was performed until an intrinsic viscosity (IV) of the mixture(melt) in the reactor became 0.60 dVg.

A content of a residue derived from 1,4-cyclohexanedimethanol withrespect to the total residue derived from a diol contained in thepolyester resin was 9 mol %.

Experimental Example 1: Evaluation of Physical Properties of PolyesterResin

The physical properties of the polyester resins prepared in PreparationExamples 1 to 9 and Comparative Preparation Examples 1 to 5 wereevaluated according to the methods described above, and the results areshown in Table 1.

In the polyester resins prepared in Preparation Examples 1 to 9 andComparative Preparation Examples 1 to 5, the remaining residue derivedfrom a diol except for the residue derived from isosorbide and theresidue derived from 1,4-cyclohexanedimethanol is derived from ethyleneglycol. The residue derived from ethylene glycol may include a residuederived from diethylene glycol introduced by reacting two ethyleneglycols to form diethylene glycol, and reacting the diethylene glycolwith a dicarboxylic acid or a derivative thereof.

TABLE 1 Residue Residue Melting derived derived temperature from fromafter Crystallization ISB CHDM crystallization Haze half-time (mol %)(mol %) (° C.) (%) (min) Mn Prep. Ex. 1 5 0 240 2 10 24,000 Prep. Ex. 210 0 235 3 55 38,000 Prep. Ex. 3 14 0 220 4 90 16,000 Prep. Ex. 4 2 5235 2 15 20,000 Prep. Ex. 5 2 8 230 3 35 18,000 Prep. Ex. 6 4 8 230 3.550 32,000 Prep. Ex. 7 3 15 220 4 75 21,000 Prep. Ex. 8 10 0 235 3 5539,500 Prep. Ex. 9 10 0 235 3 55 38,500 Comp. Prep. 25 0 NA ¹⁾ 15 >10017,000 Ex. 1 Comp. Prep. 11 11 NA ¹⁾ 20 >100 23,000 Ex. 2 Comp. Prep. 00 250 15 1 28,000 Ex. 3 Comp. Prep. 3 0 247 3 1 26,000 Ex. 4 Comp. Prep.0 9 NA ¹⁾ 2 >100 27,000 Ex. 5 ¹⁾ The polyester resins of ComparativePreparation Examples 1, 2 and 5 were amorphous resins and were notcrystallized, so that the melting temperature after crystallizationcould not be measured.

Examples and Comparative Examples: Preparation of Polyester Resin Blend

The polyester resin prepared in one of Preparation Examples 1 to 9 andComparative Preparation Examples 1 to 5 was blended with recycled PET ina weight ratio of 50:50. Specifically, recycled PET, which wasre-pelletized by melt-extruding flakes obtained by pulverizing andwashing waste plastics, was dry-mixed at roam temperature with the abovepolyester resin pelletized separately, and dried at a temperature of150° C. to prepare a polyester resin blend.

The composition of the recycled PET may vary depending on where thewaste plastics are collected, how to sort the waste plastics, and how tore-pelletize it. The recycled PET used in this experiment is a copolymerof terephthalic acid, isophthalic acid and ethylene glycol, whichcontains isophthalic acid within 3 mol % with respect to the totaldicarboxylic acid, and has an intrinsic viscosity (IV) of 0.75 dl/g, acrystallization temperature of 130° C., and a melting temperature of250° C.

Experimental Example 2: Evaluation of Physical Properties of PolyesterResin Blend

The physical properties of the polyester resin blends prepared abovewere evaluated according to the methods described above, and the resultsare shown in Table 2.

TABLE 2 Occurrence Loss 2nd melting Occurrence of flake modulus Hazetemperature of flow- fusion during onset point (%) (° C.) mark recycling(° C.) Ex. 1 3 245 X X 135 Ex. 2 1 240 X X 150 Ex. 3 1 225 X X ND²⁾ Ex.4 2 235 X X 140 Ex. 5 1 235 X X 145 Ex. 6 2 230 X X ND²⁾ Ex. 7 2.5 225 XX ND²⁾ Ex. 8 2 245 X X 145 Ex. 9 3 245 X X ND²⁾ Comp. Ex. 1 2 210 ◯ ◯ND²⁾ Comp. Ex. 2 3 220 X ◯ 135 Comp. Ex. 3 98 255 X X 100 Comp. Ex. 4 98250 X X 110 Comp. Ex. 5 50 255 X X 100 ²⁾When loss modulus onset pointwas not observed, it was indicated as ND.

Referring to Table 2, it was confirmed that Examples 1 to 9 used apolyester resin containing 5 to 20 mol % of a diol moiety derived from acomonomer including isosorbide with respect to the total diol moiety,and thus could provide a polyester resin composition having a low hazeand a melting temperature advantageous for processing by blending withrecycled PET. Particularly, it was confirmed that the polyester resinblends of Examples 1 to 9 had a high loss modulus onset point, so thatthe polyester resin according to an embodiment of the present disclosurecan effectively slow down the crystallization rate of the recycled PET,making it possible to manufacture a thick container with hightransparency.

In addition, no flow-mark was observed on the bottles in which thepolyester resin compositions of Examples 1 to 9 were processed, and thebottles were not fused even if they were left at a high temperatureafter pulverization, so that they can be reused as the resin blend.

On the other hand, in the case of Comparative Example 3 using ahomopolymer made of terephthalic acid and ethylene glycol as a polyesterresin and Comparative Example 4 using a polyester resin containing lessthan 5 mol % of a diol moiety derived from a comonomer includingisosorbide, miscibility with recycled PET was excellent, but thecrystallization rate of the recycled PET could not be lowered, resultingin a very high haze.

In addition, Comparative Example 1 using a polyester resin containingmore than 20 mol % of a diol moiety derived from a comonomer includingisosorbide had poor miscibility with recycled PET, resulting inflow-marks on the bottle prepared therefrom. Further, the flakesobtained by pulverizing the bottle were fused at a high temperature, andcould not be reused.

In addition, Comparative Example 2 using a polyester resin containingmore than 20 mol % of a diol moiety derived from a comonomer includingisosorbide and 1,4-cyclohexanedimethanol had poor miscibility withrecycled PET, resulting in flow-marks on the bottle prepared therefrom.

In the case of Comparative Example 5 using a polyester resin containinga diol moiety derived from a comonomer other than isosorbide hadexcellent miscibility with recycled PET, but the crystallization rate ofthe recycled PET could not be lowered and the haze was very high.

1. A polyester resin blend comprising polyethylene terephthalate; and apolyester resin having a structure in which an acid moiety derived froma dicarboxylic acid or a derivative thereof and a diol moiety derivedfrom a diol are repeated by polymerizing a dicarboxylic acid or aderivative thereof and a diol containing ethylene glycol and acomonomer, wherein the polyester resin comprises 5 to 20 mol % of a diolmoiety derived from a comonomer with respect to the total diol moietyderived from a diol, and the comonomer comprises isosorbide.
 2. Thepolyester resin blend of claim 1, wherein the polyethylene terephthalateis virgin polyethylene terephthalate, recycled polyethyleneterephthalate, or a mixture thereof.
 3. The polyester resin blend ofclaim 2, wherein the recycled polyethylene terephthalate has anintrinsic viscosity of 0.6 to 0.8 dVg.
 4. The polyester resin blend ofclaim 2, wherein the recycled polyethylene terephthalate comprises 95mol % or more of a residue derived from terephthalic acid and 95 mol %or more of a residue derived from ethylene glycol.
 5. The polyesterresin blend of claim 1, wherein the polyester resin is a crystallineresin.
 6. The polyester resin blend of claim 1, wherein a passing rateis 97 wt % or more, when the polyethylene terephthalate and thepolyester resin are pelletized to be 80 pieces per 1 g each, dried at atemperature of 160° C. for 1 hour, and then passed through a sievehaving a sieve size of 2.36 mm.
 7. The polyester resin blend of claim 1,wherein the polyester resin has a haze of 5% or less, when measured fora 6 mm thick specimen according to ASTM D1003-97.
 8. The polyester resinblend of claim 1, wherein the polyester resin has a melting temperatureof 210 to 245° C., when measured after crystallization at 180° C. for100 minutes.
 9. The polyester resin blend of claim 1, wherein thepolyester resin has a crystallization half-time of 7 minutes to 95minutes.
 10. The polyester resin blend of claim 1, wherein the polyesterresin comprises 0.1 to 10 mol % of a diol moiety derived from isosorbidewith respect to the total diol moiety derived from a diol.
 11. Thepolyester resin blend of claim 1, wherein the comonomer furthercomprises cyclohexanedimethanol.
 12. The polyester resin blend of claim11, wherein the polyester resin comprises a residue derived fromisosorbide and a residue derived from cyclohexanedimethanol in a ratioof 1:2 to 5 mol.
 13. The polyester resin blend of claim 1, wherein thepolyester resin blend has a melting temperature of 225 to 250° C. 14.The polyester resin blend of claim 1, wherein the polyester resin blendhas a haze of 5% or less, when measured for a 6 mm thick specimenaccording to ASTM D1003-97.